package com.scheuk.euler;

import java.util.ArrayList;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;

public class p011 {
	
	/*
	 * 2D array encoded as 1D array. Each horizontal step you take in the original 2D array corresponds
	 * a horizontal step in the 1D array. Each verical step in 2D array corresponds to skipping over 
	 * one row of elements in the 1D array. 
	 * Formula to get element at (row,col) in the 2D array in the 1D array:
	 *     row*width + col
	 *     
	 * Example of 3x3 grid2D:
	 *     1 2 3
	 *     4 5 6
	 *     6 7 9
	 * 
	 * Convert to 1x(3 by 3) grid1D: {1 2 3 4 5 6 7 8 9}
	 * 
	 * grid2D[1][1] = '5'
	 * grid1D[row*width + col] = grid1D[(1*3) + 1] = grid1D[4] = '5'
	 * 
	 */
	public static int[] grid = 
		{8, 2, 22, 97, 38, 15, 0, 40, 0, 75, 4, 5, 7, 78, 52, 12, 50, 77, 91, 8,
		49, 49, 99, 40, 17, 81, 18, 57, 60, 87, 17, 40, 98, 43, 69, 48, 4, 56, 62, 0,
		81, 49, 31, 73, 55, 79, 14, 29, 93, 71, 40, 67, 53, 88, 30, 3, 49, 13, 36, 65,
		52, 70, 95, 23, 4, 60, 11, 42, 69, 24, 68, 56, 1, 32, 56, 71, 37, 2, 36, 91,
		22, 31, 16, 71, 51, 67, 63, 89, 41, 92, 36, 54, 22, 40, 40, 28, 66, 33, 13, 80,
		24, 47, 32, 60, 99, 3, 45, 2, 44, 75, 33, 53, 78, 36, 84, 20, 35, 17, 12, 50,
		32, 98, 81, 28, 64, 23, 67, 10, 26, 38, 40, 67, 59, 54, 70, 66, 18, 38, 64, 70,
		67, 26, 20, 68, 2, 62, 12, 20, 95, 63, 94, 39, 63, 8, 40, 91, 66, 49, 94, 21,
		24, 55, 58, 5, 66, 73, 99, 26, 97, 17, 78, 78, 96, 83, 14, 88, 34, 89, 63, 72,
		21, 36, 23, 9, 75, 0, 76, 44, 20, 45, 35, 14, 0, 61, 33, 97, 34, 31, 33, 95,
		78, 17, 53, 28, 22, 75, 31, 67, 15, 94, 3, 80, 4, 62, 16, 14, 9, 53, 56, 92,
		16, 39, 5, 42, 96, 35, 31, 47, 55, 58, 88, 24, 0, 17, 54, 24, 36, 29, 85, 57,
		86, 56, 0, 48, 35, 71, 89, 7, 05, 44, 44, 37, 44, 60, 21, 58, 51, 54, 17, 58,
		19, 80, 81, 68, 5, 94, 47, 69, 28, 73, 92, 13, 86, 52, 17, 77, 4, 89, 55, 40,
		4, 52, 8, 83, 97, 35, 99, 16, 7, 97, 57, 32, 16, 26, 26, 79, 33, 27, 98, 66,
		88, 36, 68, 87, 57, 62, 20, 72, 3, 46, 33, 67, 46, 55, 12, 32, 63, 93, 53, 69,
		4, 42, 16, 73, 38, 25, 39, 11, 24, 94, 72, 18, 8, 46, 29, 32, 40, 62, 76, 36,
		20, 69, 36, 41, 72, 30, 23, 88, 34, 62, 99, 69, 82, 67, 59, 85, 74, 4, 36, 16,
		20, 73, 35, 29, 78, 31, 90, 1, 74, 31, 49, 71, 48, 86, 81, 16, 23, 57, 5, 54,
		1, 70, 54, 71, 83, 51, 54, 69, 16, 92, 33, 48, 61, 43, 52, 1, 89, 19, 67, 48};
	
	public static int[] testGrid = 
		{ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16 };
	
	public static long findMatrixProduct2(int[] grid, int height, int width, List<Long> products)
	{
		int row = 0;
		long result = 0;
		while (height > 0) {
			int index=0;
			if (height < 4) {
				while(index < (width-3))
				{
					long currentIndex = grid[(row*width)+index];
					//add right
					products.add(currentIndex * grid[(row*width)+index+1] * grid[(row*width)+index+2] * grid[(row*width)+index+3]);
					index++;
				}
				index=0;
				row++;
				height--;
			} else {
				while(index < width)
				{
					long currentIndex = grid[(row*width)+index];
					if(index < 4 && ((index+3) < width)) {
						//add right
						products.add(currentIndex * grid[(row*width)+index+1] * grid[(row*width)+index+2] * grid[(row*width)+index+3]);
						//add down
						products.add(currentIndex * grid[((row+1)*width)+index] * grid[((row+2)*width)+index] * grid[((row+3)*width)+index]);
						//add diagonal right
						products.add(currentIndex * grid[((row+1)*width)+index+1] * grid[((row+2)*width)+index+2] * grid[((row+3)*width)+index+3]);
					} else if (index > 3 && index < (width-3)) {
						//add right
						products.add(currentIndex * grid[(row*width)+index+1] * grid[(row*width)+index+2] * grid[(row*width)+index+3]);
						//add down
						products.add(currentIndex * grid[((row+1)*width)+index] * grid[((row+2)*width)+index] * grid[((row+3)*width)+index]);
						//add diagonal right
						products.add(currentIndex * grid[((row+1)*width)+index+1] * grid[((row+2)*width)+index+2] * grid[((row+3)*width)+index+3]);
						//add diagonal left
						products.add(currentIndex * grid[((row+1)*width)+index-1] * grid[((row+2)*width)+index-2] * grid[((row+3)*width)+index-3]);
					} else if ((index >= 3 ) && (index==(width-1) || index==(width-2) || index==(width-3))) {
						//add down
						products.add(currentIndex * grid[((row+1)*width)+index] * grid[((row+2)*width)+index] * grid[((row+3)*width)+index]);
						//add diagonal left
						products.add(currentIndex * grid[((row+1)*width)+index-1] * grid[((row+2)*width)+index-2] * grid[((row+3)*width)+index-3]);
					} else {
						//add down
						products.add(currentIndex * grid[((row+1)*width)+index] * grid[((row+2)*width)+index] * grid[((row+3)*width)+index]);
					}
					index++;
				}
				index=0;
				row++;
				height--;
			}	
		}
		Collections.sort(products);
		long product = (Long) products.get(products.size()-1);
		result = (product > result) ? product : result;
		return result;
	}

	public static void main(String[] args) {
		List<Long> results = new ArrayList<Long>();
		System.out.println("answer is for 4x4 test grid : " + p011.findMatrixProduct2(p011.testGrid, 4, 4, results));
		results.clear();
		System.out.println("answer is for 20x20 gride : " + p011.findMatrixProduct2(p011.grid, 20, 20, results));

	}
}
